Multicomponent extendible structures are by no means new, and they have found many useful applications. Such structures have been utilized both on the ground and in space to provide rigid or semirigid extended structures which can be utilized as antennas or as booms for extending or retracting various types of equipment or to elevate and retract various types of equipment.
One of the primary advantages of a multicomponent extendible structure is that it comprises two or more elongated thin sheets of material which are capable of being rolled or otherwise compacted into a small compact package. As a consequence a multicomponent extendible structure need take up very little space when it is in its stored or packaged configuration and yet it is capable of being extended to form an elongaged structure of considerable length. This ability to transform itself from a small compact stored configuration into a comparatively large operational configuration makes such multicomponent extendible structures particularly attractive for use where it is necessary to have a compact configuration due to a limited capacity or volume for the extendible structure. This is particularly for such applications such as military antennas and the like where it is desirable to stow an antenna or the like in a small package when it is not in use since there may be only limited storage space available such as on a military vehicle.
One of the problems associated with such multicomponent extendible structures has been how to obtain a rigid structure when the multicomponent extendible structure is in its extended configuration. In this connection it is desirable that the extended multicomponent extendible structure have some type of cross section that lends rigidity to the extended structure. Such a cross section might take the form of a triangle, rectangle or the like. In order to obtain such a cross section it is necessary to interconnect the edge portions of the elongated sheets of material which form the multicomponent extendible structure. It is also important that the edges of these elongated sheets be securely fastened so that they cannot be pulled apart. Otherwise the multicomponent extendible structure would lose its rigidity and strength.
Various techniques have been tried in the past for fastening the edges of two or more elongated sheets of material together. One type of method of attachment is set forth in U.S. Pat. No. 3,503,164 which discloses a tubular extendible structure that is formed from two elongated sheets of material that have tabs and slots on the edges for joining the elongated sheets of material together. It should be noted however that the tubular extendible structure set forth in this patent is designed to have the tabs remain in the slots during the time that the tubular extendible structure is rolled into its stored compact configuration as well as when it is in its extended position. This may be somewhat satisfactory when there are only two elongated sheets of material involved and it is only desired to have a simple ring shaped or circular shaped cross section. However, for more complex structures which involve more than two elongated sheets, it is generally necessary to separate the sheets for storage purposes such as illustrated in U.S. Pat. No. 3,319,987 where the elongated sheets or strips are separated or rolled on a plurality of rollers. As illustrated in this patent the plurality of elongated sheets of material are fastened together by tongues and slots located along the respective edges of material. It should be noted however that these tongues and slots do not provide in themselves an edge locking system that prevents the edges of the adjacently located elongated sheets from being pulled apart when the multicomponent extendible structure is in its extended configuration.
These problems associated with the structures set forth in U.S. Pat. Nos. 3,503,164 and 3,319,987 have been largely overcome by the multicomponent extendible structure disclosed in U.S. Pat. 4,386,485. The invention set forth in this patent includes a multicomponent extendible structure that permits a plurality of elongated sheets of material to be separately and compactly stored but joined by securely joining the elongated sheets together at their edges when the multicomponent extendible structure is extended into its operational configuration.
While the invention set forth in U.S. Pat. No. 4,386,485 overcomes many of the problems associated with previous prior art structures, it is desirable to have an increased ability to withstand compressive loads and to have the ability to withstand tension loads. This is particularly true when the extendible structure is to be used to elevate heavy loads in a one g environment and where the extended structure will be exposed to large side loads such as would occur when the extended structure is exposed to strong winds or when it is extended at an angle. The latter could easily occur if the extendible structure was extended from a vehicle that was not on completely flat land.
The present invention overcomes the strength problems associated with the prior art extendible structures and provides an extendible multicomponent structure that has all of the advantages of the structure set forth in U.S. Pat. No. 4,386,485 but has exceptionally good resistance to compressive loads as well as tensional loads.